The present invention relates to coronary augmenters and, in particular, to systems for contracting skeletal muscles to affect blood flow and cardiac health in a cardiac patient and prevention of coronary artery disease in normal or high risk groups.
It is known to apply a tetanizing current across skeletal muscles of a patient who may be suffering from ailments such as tendonitis, neuritis, bursitis, or other muscle ailments. This therapy involves applying an alternating current across the muscle to contract it involuntarily for a predetermined interval, for example, five (5) minutes. However, this type of instrument has not been used nor proposed as a device for treating coronary disease.
It is also known that properly scaled exercise can affect the health of the heart. Research has also shown that exercise at an appropriate level can cause natural production by the body of sympathomimetic amines such as catecholamines. These catecholamines when placed into circulation can increase the contracting strength of muscles and dilate blood vessels supplying these muscles.
Various devices and appliances have been proposed for assisting a weakened myocardium. Such coronary augmenters have been disclosed in the literature; for example Hauser and Carleton, The Failing Myocardium, Symposium on Coronary Heart Disease, Medical Clinics of North America, Vol. 57, No. 1, January, 1973, at pp. 187-204; Giron, Rationale and Early Experience in Assisted Circulation, Department of Surgery, The Bronx Veterans Administration Hospital, Bronx, N.Y., 10468, at pp. 160-167; Weber at. al., An Assessment of Intra-Aortic Balloon Pumping in Hypovolemic and Ischemic Heart Preparations, The Journal of Thoracic and Cardiovascular Surgery, Vol. 64, No. 6, December 1972, at pp. 869-877. These references also disclose counterpulsation techniques for mechanically assisting the left ventricle. One known method involves an intra-aortic balloon which is inserted as a catheter into the femoral artery and routed into the aorta near the left ventricle. A pulsating source of pressurized carbon dioxide is used to quickly inflate and deflate the intra-aortic balloon. This repetitive action is triggered by an electrocardiac signal taken from the patient in a fashion similar to a standard electrocardiogram. This intra-aortic balloon is deflated during systole to relieve back pressure and to prevent the pump from working against the heart. During diastole, the balloon is reinflated thereby assisting the pumping action of the heart and also causing a back pressure tending to drive blood into the coronary arteries.
The literature has suggested that the myocardium has a capacity to bypass occluded coronary arteries by developing collateral circulation. The higher pressure heads caused by occluded arteries diverts blood through minor vessels and capillaries which consequently expand to provide a secondary bypass. Discussion of this phenomenon can be found in: Levin et. al., Coronary Collateral Circulation and Distal Coronary Run-Off, The American Journal of Roentgenology, Radium Therapy and Nuclear Medicine, Vol. 119, No. 3, November 1973, at pp. 463-473; Baroldi and Scomazzoni, Coronary Circulation in Normal and Pathological Heart, Office of Surgeon General, Department of Army, Washington, D.C., 1967; Knobel et. al., Myocardial Blood Flow in Coronary Artery Disease, Circulation, Vol. 47, April 1973, at pp. 690-696.
Another method of diastolic augmentation which is non-invasive employs a hydraulic boot in the form of a box surrounding the lower extremities of the patient. A bladder surrounding the extremities is inflated and deflated at a rate proportional to heartbeat. However, this method requires a relatively large hydraulic device having the disadvantages of being slow, heavy, and expensive. It is also a purely mechanical technique which does not at all involve body chemistry in the therapeutic treatment of the ailing myocardium.
Also, significant research has been undertaken to determine the effect of the phasing of inspiration and expiration on the heart. It has been suggested that proper phasing can increase the efficiency of the heart. Accordingly, research has been conducted to determine the effect of such respiratory phasing and also the effect of breathing apnea and respiratory paralysis from any cause. See for example, Horvat et. al., Effect of Oxygen Breathing on Pacing-Induced Angina Pectoris and Other Manifestations of Coronary Inefficiency, Circulation, Vol. 45, 1972, at p. 837; Pigott and Spodick, Effects of Normal Breathing and Expiratory Apnea on Duration of the Phases of Cardiac Systole, American Heart Journal, Vol. 82, No. 6, December, 1971, at pp. 786-793. Furthermore, this relative phasing of respiration has been considered important for a heart-lung machine. Also, research has been conducted to effect involuntary diaphragm contraction and pace respiration by means of stimulation to the phrenic nerve of a patient.
Accordingly, there is a need for apparatus and methods to treat and assist a diseased heart either in grave cases to sustain life or on a regular basis for normal patients interested in weight control, exercise and its therapeutic value. Such equipment and methods should be simple, effective, safe and sufficiently flexible to be used on various patients.